Reconciliation of income tax computed at US Federal tax rates (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Abstract]
Statutory Income Tax	21.00%	21.00%	21.00%
Net Operating Loss Carryback	(3.80%)	0.00%	0.00%
Deemed Repatriation Tax on Foreign Earnings and Profit	0.00%	0.00%	1.80%
Tax Exempt Income	(0.80%)	(0.50%)	(1.30%)
Tax Credits	(1.30%)	(1.10%)	(2.40%)
Policyholder Reserves	0.70%	0.00%	(2.40%)
Other Items, Net	1.90%	1.00%	(0.10%)
Effective Tax	17.70%	20.40%	16.60%